The electric field of an optical pulse can be described in the time domain or in the frequency domain. The spectral phase of an optical pulse is the phase of the electric field in the frequency domain. Ultrashort optical pulses are those optical pulses having durations of femtoseconds or picoseconds and high peak intensity. In ultrafast optics, an optical pulse is transform limited if it has a frequency-independent (and therefore wavelength-independent) spectral phase. For a given pulse duration, transform-limited pulses are those with the minimum possible temporal width. The pulse duration of ultrashort optical pulses can be sensitive to various effects, such as chromatic dispersion, nonlinearities, and optical filters.